I bought a new Mossberg 500 last week with both the 28" barrel and the 24" rifled slug barrel. I shot 3 #8 dove loads through the long barrel and it worked slick and smooth. I then put the slug barrel on it and shot it twice. I used Hornaday SST sabot slugs. They shot accurately but the empty shells were very hard to eject. At first, I thought I had a malfunction. I then changed barrels, tried more of the #8 shot and it again worked great. Is this normal or have I done something wrong?